src/net/iobpad.c

   1 /*
   2  * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  *
  19  * You can also choose to distribute this program under the terms of
  20  * the Unmodified Binary Distribution Licence (as given in the file
  21  * COPYING.UBDL), provided that you have satisfied its requirements.
  22  */
  23
  24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  25
  26 /**
  27  * @file
  28  *
  29  * I/O buffer padding
  30  *
  31  */
  32
  33 #include <string.h>
  34 #include <ipxe/iobuf.h>
  35
  36 /**
  37  * Pad I/O buffer
  38  *
  39  * @v iobuf             I/O buffer
  40  * @v min_len           Minimum length
  41  *
  42  * This function pads and aligns I/O buffers, for devices that
  43  * aren't capable of padding in hardware, or that require specific
  44  * alignment in TX buffers.  The packet data will end up aligned to a
  45  * multiple of @c IOB_ALIGN.
  46  *
  47  * @c min_len must not exceed @v IOB_ZLEN.
  48  */
  49 void iob_pad ( struct io_buffer *iobuf, size_t min_len ) {
  50         void *data;
  51         size_t len;
  52         size_t headroom;
  53         signed int pad_len;
  54
  55         assert ( min_len <= IOB_ZLEN );
  56
  57         /* Move packet data to start of I/O buffer.  This will both
  58          * align the data (since I/O buffers are aligned to
  59          * IOB_ALIGN) and give us sufficient space for the
  60          * zero-padding
  61          */
  62         data = iobuf->data;
  63         len = iob_len ( iobuf );
  64         headroom = iob_headroom ( iobuf );
  65         iob_push ( iobuf, headroom );
  66         memmove ( iobuf->data, data, len );
  67         iob_unput ( iobuf, headroom );
  68
  69         /* Pad to minimum packet length */
  70         pad_len = ( min_len - iob_len ( iobuf ) );
  71         if ( pad_len > 0 )
  72                 memset ( iob_put ( iobuf, pad_len ), 0, pad_len );
  73 }